Monoplace hyperbaric chambers are designed to provide oxygen therapy under a specific pressure profile for one patient at a time. Such chambers typically have basic pressure control and monitoring systems. A commercially available example of a conventional chamber is the Model 3200 Monoplace Hyperbaric Chamber manufactured by Sechrist Industries, Inc. of Anaheim, Calif. These chambers typically include a series of manual gas valves that allow an operator to control input pressure, ventilation, and exhaust. Conventional chambers require the use of a large volume of oxygen in order to maintain the desired pressure while attempting to provide adequate ventilation to control carbon dioxide and water vapor and provide patient cooling. For example, a typical prior art monoplace hyperbaric chamber uses 200 to 500 liters per minute of oxygen.
Turning to FIG. 1, a pneumatic schematic illustrating a convention system 100 of flow control gas valves for a typical prior art hyperbaric chamber 102 is depicted. An oxygen supply 104 feeds the chamber 102 with oxygen to create compression in the chamber 102. The desired amount of oxygen is applied at a rate controlled via a pressure flow control valve 106. The pressure flow control valve 106 is itself controlled by a pneumatic control signal that may be adjusted to an appropriate pressure by referencing a pressure gauge 108. A regulator 110 is used to actually send the pneumatic control signal to the pneumatic control of the pressure flow control valve 106 to allow more or less oxygen into the chamber 102. The operator must carefully monitor the chamber pressure by watching the chamber pressure gauge 120 relative to the pneumatic control signal on the first pressure gauge 108.
In addition to the pressure flow control valve 106, a ventilation flow control valve 112 is used to provide additional oxygen to the chamber 102 for ventilation. The ventilation flow control valve 112 is controlled based upon the current amount of pressure in the chamber 102 via a feedback pneumatic control signal to the ventilation flow control valve 112.
An exhaust flow control valve 114 (e.g., a back pressure flow control valve) vents air from the chamber 102 at a rate that is slow enough to maintain the desired pressure within the chamber 102 but fast enough to both meet a required ventilation rate and help maintain a desired temperature range within the chamber 102. Thus, the pneumatic control of the exhaust flow control valve 114 also receives a feedback pneumatic control signal based upon the current amount of pressure in the chamber 102. Finally, the exhaust circuit also includes a manual bypass exhaust flow control valve 116 and a flow meter 118 to allow manual release of compressed air from the chamber 102 at a manually controlled rate.
A significant problem with prior art hyperbaric chamber control systems is that they require equally zeroed and calibrated pressure gauges at atmospheric pressure to not read the same pressures for a given treatment depth. For example, the prior art requires a substantial (e.g., ½ to 1 PSIG) differential between a lower set pressure and a desired chamber treatment pressure in order for the prior art system to provide a 200 lpm+ ventilation rate. This necessary miscalibration has often resulted in operator confusion due to the difference between the gauges which may result in operator error that may compromise patient care.
As depicted in FIG. 2, in prior art hyperbaric chambers 102, incoming oxygen will find the least resistive route 200 to the exhaust port. This phenomenon is referred to as a channeling effect. Unless a very high volume (e.g., 200+ lpm) of oxygen is forced into the prior art chamber 102, the majority of the oxygen in the chamber 102 being exhausted will bypass the patient 202 and flow below or between the stretcher 204 and the chamber hull. Below 200 lpm prior art chambers fail to ventilate causing fogging due to water vapor from the patient's breathing and causing a build-up of carbon dioxide in the chamber 102. Thus, prior art chambers 102 must use a high volume of oxygen to insure adequate circulation of oxygen within the chamber 102. This further contributes to the inefficiency of prior art hyperbaric chambers 102. In many prior art chambers 102, adequate circulation is not only important in order to provide the patient 202 with sufficient oxygen for breathing and to remove exhaled carbon dioxide and water vapor, but also to maintain a comfortable temperature throughout the chamber 102.
In many areas of the world, medical grade compressed oxygen suitable for use in a hyperbaric chamber 102 is expensive and not readily available. Thus, it is a substantial drawback of prior art chambers 102 that they must use high volumes of oxygen. In addition, using such high volumes of oxygen results in significant noise levels within the chamber 102 which may be unpleasant for patients that may be subjected to the loud noise for prolonged periods during treatment. Thus, what is needed is a monoplace hyperbaric chamber and control system that does not suffer from the above described drawbacks.